TF front axle shims?

[roger55]

I've installed a CPP 400 power steering box in my '57. I'm keeping the straight axle and stock springs both in the front and rear of the truck.

I want to put some positive caster in it for a better steering feel. I've been told that with power steering I want about 4 degrees of positive caster. I'm about ready to install the front axle back onto the frame after blasting and painting everything.

Can I choose which shims I need now? Are these TF trucks 0 degrees caster without any shims?

Or, should I just install the axle now with no shims and wait until until the entire truck is assembled and measure the caster and then go from there?

Btw, when I disassembled the front end, it had 1 degree shims installed. But, they were installed in the direction to decrease the caster. I wonder if a previous owner did that to make it steer easier or if it was factory.

[mr48chev]

First you have to find out exactly what caster you have now. Then figure out what change if any you need to make. That usually takes a trip to a front end shop unless you have access to a caster/camber gauge.

There is probably an old school shop in San Angelo that has a stick on the hub gauge to check it with that doesn't charge a fortune like the fancy places with the wizz bang 4 wheel alignment electronic machines. Or if you have some buddies with circle track cars a lot of circle trackers have their own caster camber gauges in their tool boxes.

Someone will no doubt come on and tell how to do it with rocks, sticks and string or something but those home brewed systems don't always work the way you want them too nor are they anywhere near accurate.

Take a look between the springs and axle to see if there are already shims in there as they were quite often shimmed to get the trucks to track better on the road years ago. The shims are readily available in a variety of degrees.

[roger55]

Originally Posted by mr48chev

First you have to find out exactly what caster you have now. Then figure out what change if any you need to make. That usually takes a trip to a front end shop unless you have access to a caster/camber gauge.

There is probably an old school shop in San Angelo that has a stick on the hub gauge to check it with that doesn't charge a fortune like the fancy places with the wizz bang 4 wheel alignment electronic machines. Or if you have some buddies with circle track cars a lot of circle trackers have their own caster camber gauges in their tool boxes.

Someone will no doubt come on and tell how to do it with rocks, sticks and string or something but those home brewed systems don't always work the way you want them too nor are they anywhere near accurate.

Take a look between the springs and axle to see if there are already shims in there as they were quite often shimmed to get the trucks to track better on the road years ago. The shims are readily available in a variety of degrees.

Thing is that I can't do any measuring now. The frame is stripped bare and has been blasted and painted and I'm beginning the assembly process right now. The springs are new (stock height) and I just installed them on the frame yesterday. Now I'm ready to install the front axle. Also, like I said, when I disassembled the axle, it had 1 degree shims in it but they were installed in the direction to decrease the caster. But, there was no power steering before and the PO probably didn't want much if any positive caster to make it steer easier. The PO had also added a leaf to the original springs.

However, I understand what you are saying. I think what I might do is install 4 degree shims as a guess. When the truck is drivable (about a year from now), I can then go to an alignment shop to get it checked. With 4 degree shims in there, I have a better shot of having it be close enough to what I want than I would if I don't install any shims now saving me the work of taking it all apart again later.

[mr48chev]

If it were me I'd just put the 1 degree shims in correctly and go get it checked after it was all together. The thick part of the wedge goes towards the front of the truck to lay the axle back a bit. Then it won't be a big deal if you decide you want more caster after you drive it a bit and change to add more caster to it. With everything cleaned up you can change shims in about 15 minutes and only have to loosen the U bolt nuts far enough to let the axle drop down so you can get the shims out and back in.

The reason I am suggesting doing it this way is that 4 degree shims may end up giving you 6 degrees of caster if the truck already has 2 degrees in it when you put it back together due to having the new springs in. And you don't know why a P/O had the shims put in to reduce caster but most likely it was to reduce steering effort a bit as the truck already had quite a bit of caster in it.

[roger55]

Originally Posted by mr48chev

If it were me I'd just put the 1 degree shims in correctly and go get it checked after it was all together. The thick part of the wedge goes towards the front of the truck to lay the axle back a bit. Then it won't be a big deal if you decide you want more caster after you drive it a bit and change to add more caster to it. With everything cleaned up you can change shims in about 15 minutes and only have to loosen the U bolt nuts far enough to let the axle drop down so you can get the shims out and back in.

The reason I am suggesting doing it this way is that 4 degree shims may end up giving you 6 degrees of caster if the truck already has 2 degrees in it when you put it back together due to having the new springs in. And you don't know why a P/O had the shims put in to reduce caster but most likely it was to reduce steering effort a bit as the truck already had quite a bit of caster in it.

I really appreciate your help on this. It's helped my thought processes a lot.

Before you made this last post this morning, I had already ordered a pair of 4 degree shims for $17 off of ebay.

I think I'm going to go ahead and install those instead of the 1 degree ones I have. I had a guy tell me that he set up a '57 Suburban with 6 degrees of caster with power steering and it drives great. So, if I end up with 6, I think that will be OK. If it ends up anywhere between 4 and 6, I'll leave it.

[Russell Ashley]

Originally Posted by roger55

I really appreciate your help on this. It's helped my thought processes a lot.

Before you made this last post this morning, I had already ordered a pair of 4 degree shims for $17 off of ebay.

I think I'm going to go ahead and install those instead of the 1 degree ones I have. I had a guy tell me that he set up a '57 Suburban with 6 degrees of caster with power steering and it drives great. So, if I end up with 6, I think that will be OK. If it ends up anywhere between 4 and 6, I'll leave it.

The thick end of the shim will go to the rear to increase castor. You want the top of the king pin inclined towards the rear to increase castor.

I also have 6 degree shims in my 57 truck with CPP power steering kit but I don't know what the actual castor would be if measured by an alignment shop. It did seem to track a little better after I put them in but it was not a major difference that I could tell.

[dubie]

The only reason to adjust the caster by anything more than 1 degree would be if the truck was lower 3-6" from stock ride height. Being that yours is stock height and all you're doing is adding in a power steering unit, shouldn't make that much of a difference. I lowered mine 6" and the difference between driving with a shim and without, was extremely noticeable.
Did you drive the truck before tearing it down or was this a rebuild project from the start. If you did drive it before, did the steering wheel always come back to center after you turned a corner? Did the truck track straight and true(as straight and true as a kingpin truck can go) no matter what the speed? If so, then I would put the 1 degree shim back in, just to return it to the way it was. Then take the truck for a test drive. Once you drive it, you'll get a fell for everything. Your next stop after that should be for an alignment

[roger55]

Originally Posted by Russell Ashley

I also have 6 degree shims in my 57 truck with CPP power steering kit but I don't know what the actual castor would be if measured by an alignment shop. It did seem to track a little better after I put them in but it was not a major difference that I could tell.

It's possible you have 7 or 8 degrees of caster.
Does it track pretty well?

Curious, do you have the CPP 400 box or did you get the GM box that mounts outside the frame?

[Russell Ashley]

I have the box that mounts outside of the frame. I bought the CPP kit a few years ago before I knew better, I don't recommend it. It has some bump steer which I think is caused by the short drag link. I could possibly move the box to lengthen it and help some but I've already made up my mind to get rid of the straight axle after the first of the year..

When driving down a straight smooth road it tracks fine. I do think the caster shims helped that. My front springs are original as far as I can tell but have sagged to the point that my truck has a slight forward rake. The springs are almost straight, with about 1.5 inches between the bump stops. If it originally had 1.5 degrees of caster as specified in the service manual, I think the rake would have negated that, so that the 6 degree shims would give me an actual 6 degrees of caster. I would have to take it to an alignment shop to find out exactly but since I'm going to dump the axle I won't bother to do that.
BTW: I think I have read somewhere that they increased the caster to 4 degrees when the truck had power steering, but can't remember where I saw it.

[roger55]

Originally Posted by Russell Ashley

I have the box that mounts outside of the frame. I bought the CPP kit a few years ago before I knew better, I don't recommend it. It has some bump steer which I think is caused by the short drag link. I could possibly move the box to lengthen it and help some but I've already made up my mind to get rid of the straight axle after the first of the year..

When driving down a straight smooth road it tracks fine. I do think the caster shims helped that. My front springs are original as far as I can tell but have sagged to the point that my truck has a slight forward rake. The springs are almost straight, with about 1.5 inches between the bump stops. If it originally had 1.5 degrees of caster as specified in the service manual, I think the rake would have negated that, so that the 6 degree shims would give me an actual 6 degrees of caster. I would have to take it to an alignment shop to find out exactly but since I'm going to dump the axle I won't bother to do that.
BTW: I think I have read somewhere that they increased the caster to 4 degrees when the truck had power steering, but can't remember where I saw it.

Thanks Russell.
Yes, many articles and people recommend 4 to 5 degrees with power steering whether it be with a straight axle or independent.